Visible blade load break switch



Nov. 3, 1970 QLOSTE 3,538,273

VISIBLE BLADE LOAD BREAK SWITCH Filed Dec. 6, 1967 5 Sheets-5heet 1 IINVENTOR. (LA EK A. 0575/? Nov. 3, 1970 Filed Dec. 6, 1967 C. L. OSTERVIS IBLE BLADE LOAD BREAK SWITCH IIIIII I 5 Sheets-Sheet 2 INVENTOR.

(ZAEK A. 0572- Filed Dc. a, 1967 NOV. 3, 1970 c, QSTER 3,538,273

VISIBLE BLADE LOAD BREAK SWITCH 5 Sheets-Sheet 3 & t w

\ Q w W x Q'N wk IN VE'NZ'OR CA/IEK Z. OfTE Q W A 'TTOENEY Nov. 3, 1970c. L. OSTER 3,538,273

(VISIBLE BLADE LOAD BREAK SWITCH Filed Dec. 6, 1967 5 Sheets-Sheet 4INVENTOR. C'AAEK L. 0375/? 2 A 7 TOP/VB.

Nov. 3, 1970 C.L.OSTER I ,5 73

VISIBLE BLADE LOAD BREAK SWITCH Filed Dec. 6, 1967 5 Sheets-Sheet 5 FLAf6 t/W! i 2 wr L'E f 133m "M441 T r 31/38/ (2 Q4 Q6 (49 \36 (A/WK L.2???? /ITTOF/VEK United States Patent 3,538,273 VISIBLE BLADE LOAD BREAKSWITCH Clark L. Oster, Cedar Rapids, Iowa, assiguor to Square D Company,Park Ridge, Ill., a corporation of Michigan Filed Dec. 6, 1967, Ser. No.688,447 Int. Cl. H01h 13/28 US. Cl. 20067 11 Claims ABSTRACT OF THEDISCLOSURE The present switch is a visible blade type load break switchwhich is normally driven to open and closed positions, respectively,with a snap action by a dead-center spring mechanism operable bymanipulation of an operating handle. The snap action mechanism isarranged so that in the event of failure of its springs it can be drivenpositively and directly by the handle to close the switch and to openthe switch fully so that the blades are disposed outwardly beyond thearc stack of the switch.

The dead-center mechanism comprises two dead-center plates, juxtaposedface to face, which swing about offset parallel pivots, one plate beingmovable initially by the operating handle and, in turn, driving a pinfor operating a blade-carrying cross bar, the pin, in turn, also drivingthe other plate. Dead-center springs are connected to the plates fordriving them to fully open and close the switch, selectively, with asnap action when one of the plates has been moved by an operating handlebeyond a predetermined position. The mechanism is so arranged that itprovides a positive drive of the plates directly by the bandle foreffecting the positive drive of the blades to fully open or fully closedposition, selectively, by the handle in event of the failure of thesprings.

The movable blades are arranged so that they can be snapped intoinstalled position in a movable cross bar and can readily be detachedtherefrom while the cross bar is installed in the housing. The cross baritself is readily removable from the housing for replacement.

The switch mechanism is enclosed in an insulating housing which whensupported on its supporting frame is in overlying, protecting andconcealing relation to the mechan1sm.

The parts are devised so that the switch can be converted for right handor left hand operation by simply repositioning the handle anddead-center plates.

The switch is adapted to be used unfused, or fused with variouscombinations of fuses of different lengths and diameters, as desired.

This invention relates to a load break switch adapted for use in controlcenters in fused or unfused condition. The switch employs rigid contactblades, as distinguished from contact shoes, which are mounted in ahousing so they will be readily visible in the operating position of theswitch. Various parts of the switch are so arranged that the switch canreadily be converted to right hand or left hand merely by repositioningsome of the parts.

An important object of the invention is to provide a switch employing adead-center spring mechanism which is operable by an operating handle,and arranged so as to fully close and fully open the switch with a snapaction in normal operation, and to be driven positively by the handlefor moving the blades to fully open and fully closed position in theevent of failure of the springs.

More specific advantages reside in the manner of mounting the blades ina molded cross-bar so that the blades can be readily installed orremoved by snapping them into sockets therein without removing thecross-bar from ice the switch, and further provide for ready removal ofthe cross-bar as a whole from the switch.

Another specific object is to overlie, protect and conceal the operatingmechanism and snap acting mechanism by the blade supporting housing.

Various other specific objects and advantages of the invention willbecome apparent from the following description wherein reference is madeto the drawing, in which:

FIG. 1 is a front elevation of a switch embodying the principles of thepresent invention, with a fuse plate attached;

FIG. 2 is a right side elevation, on a reduced scale, of the switch andfuse plate illustrated in FIG. 1;

FIG. 3 is a cross sectional view of the switch and is taken on the line3-3 in FIG. 1, the fuse plate being omitted for clearness inillustration;

FIG. 4 is a bottom plan view of the switch illustrated in FIG. 1, thefuse plate being omitted;

FIG. 5 is an enlarged front elevation of the cross bar used in theswitch for carrying the movable contact blades;

FIG. 6 is a bottom plan view of the cross bar illustrated in FIG. 5;

FIG. 7 is a vertical cross sectional view of the cross bar taken on theline 7-7 in FIG. 5

FIG. 8 is a front elevation of the rear supporting frame of the switchwith the cross bar operating mechanism mounted thereon, the switch anddead-center springs for the mechanism being omitted for clearness inillustration;

FIG. 9 is a bottom plan view of the structure illustrated in FIG. 8,part thereof being broken away for clearness in illustration; and

FIG. 10 is a fragmentary view similar to FIG. 8 showing the drivingplates of the cross bar operating mechanism and dead-center springsthereof in one operating position, the position of the plates in theother operating position being indicated indot and dash lines.

Referring to FIGS. 1 and 2, the switch comprises a main housing or body1 of rigid insulating material, such as hard rubber, phenolic, or thelike preferably molded in one piece. The body is mounted on a metalsupporting frame in the form of a rear plate 2 having lateral forwardlyextending walls 3 which are disposed along the side walls of the body,respectively, and spaced outwardly therefrom, as best illustrated inFIGS. 1, 2' and 8, over the major portion of their facial extent.

The body is open at the front and is provided with channels 4!- whichare open downwardly and at their forward ends. Stationary contacts 5 aremounted in the channels, respectively, and are adapted to receive themovable contact blades -6 which are carried on a cross bar 7 of rigidinsulating material. Suitable forward barrier walls 8 are providedaround the front entrances to the channels 4 and are stacks 9 areprovided within the channels rearwardly from the barrier walls 8.

Each of the stationary contacts 5 is in the form of a forwardly openyoke between the arms of which the associated movable contact is drivenand removed by rocking of the cross bar 7. Each of the contacts 5 isconnected to a line terminal 10 which, at its upper end, is adapted tobe connected by a screw 11 to an external conductor. The line terminal10 is suitably secured in the body 1 by terminal screws 12.

The cross bar 7 is provided at its ends with trunnions l4 and is held inposition within the body 1 by engagement of the trunnions 14 withinsuitable bearing apertures 15 in the side walls 3, respectively, of theframe 2. Rocking of the cross bar about its axis, in the clockwisedirection in FIG. 3, makes contact between the movable contact blades 6and associated contacts 5. Each contact blade 6 is connected by aflexible conductor 16 to a load terminal 18 secured in the body 1 andprovided with a connector 19 for connecting an external conductor thereto. The flexible conductor 16 is brazed or soldered at its op osite endsto an associated blade 6 and load terminal 18, respectively.

Alternatively, in a manner later to be described, the contact blades '6may be connected by the flexible conductor 16 directly to a fuse platewithout use of the load terminals 18 and connectors 19.

It is desirable that the blades be readily connectable to, anddisconnectable from, the cross bar 7. For this purpose, the bar isprovided with a plurality of sockets 20 arranged in a row along the barand extending generally radially of the axis thereof. For providing asnap fastening connection between each blade 6 and the bar 7, each bladeis provided with a notch 22 and the bar, at each socket, is providedwith a shoulder 24. A snap fastener 25 in the form of a strip of springsteel has one J-shaped end 26 which can be snapped into the notch 22and, extending from the end 26, an arm portion 28 which engages theshoulder 24. The blade has a part of its forward edge offset rearwardlyof the blade, as at 29, for accommodating the portion 28 of the snapfastener 25 during the insertion of the blade lower end foremost intothe socket 20 with the snap fastener 25 installed therein. When theupper end of the portion 28 reaches the shoulder 24, it springsforwardly and bears endwise of the spring thereagainst to preventdisplacement of the blade 6. The cross bar has forwardly open slits 30,arranged one for each socket through which the blade of a screwdrivermay be inserted into the associated socket. If it is desired to changeblades for any reason, the screwdriver blade can be passed through theslit 30 and caused to engage with the portion 28 of the snap fastenerand push it back into the clearance space provided by the offset 29 sothat the end of the portion 28 is disengaged from the shoulder 24 so asto permit the blade with the snap fastener attached to be withdrawn fromthe socket.

It is necessary to rock the cross bar for moving the blades 6 with asnap action to contact-making position and to open position. Further, itis necessary that in the open position the outer or free end of eachblade 6 be disposed outwardly from its associated channel beyond the arcstack and within the confines of the barrier walls 8.

In order to assure these movements, a snap action mechanism, indicatedgenerally at 31, is provided. In the switch shown for purposes ofillustration, the snap action mechanism 31 is mounted on the metal plate2 of the metal frame so that it is concealed behind the rear of the body1 and protected thereby during normal operation. Since a snap action forboth making and breaking contact is desired, two dead-center plates 34and 35 are provided. For mounting the plates in operating position, theplates are disposed in face to face juxtaposition with operatingclearance and are supported in this position on the plate 2. For thispurpose, laterally offset bosses 36 and 38, facing forwardly from theplate 2, are provided. The plates are arranged with plate 34 juxtaposedagainst the bosses and the plate 35 disposed forwardly thereof. Theplate 34 is pivotally connected to the boss 36 by a pivot 39. The plate35 is connected to the boss 38 by a pivot 40. Each plate can swing aboutthe axis of its associated pivot independently of the other plate. Theplate 34 has a slot 41 which is of constant radius and curvilinear aboutthe axis of the pivot 39. Correspondingly, the plate 35 has a slot 42 ofconstant radius and curvilinear about the axis of the pivot 40. Thepivot 39 extends through the slot 42 and has an enlarged head 39a whichhelps to hold the plates in juxtaposition. Correspondingly, the pivotextends through the slot 41, and has an enlarged head 40a for a likepurpose. The slot of each plate is such that the pivot of the oppositeplate can slide therein endwise of the slot as each plate swings aboutits pivot relative to the other plate.

In order to operate the switch, one of the plates, for example, theplate 35, is provided at the end opposite to pivot 40 with a pluralityof radial teeth or fingers 44. Mounted on a suitable pivot pin 45 andextending inwardly from one of the side walls 3 is an operating lever 46which is disposed in the clearance space between the wall 3 and adjacentside of the body. At its outer end the lever 46 carries spaced fingersor teeth 46a which, as the lever is rocked about its axis, can mesh inthe manner of a gear with the fingers 44 to swing the plate 35 to andfro about its axis. The lever 46 is provided with means for rocking itabout its axis sufliciently to move the blades 6, through the medium ofthe plates 34 and 35 and connection with the cross bar 7, to fully openand closed positions.

It overload release devices are to be used with the switch, then suchdevice may be connected by a suitable link to the lever 46. However, inthe form illustrated, the lever 46 is provided with a handle 47 formanual operation.

The plates 34 and 35 are so connected to each other that when the plate35 is swung clockwise about its pivot '40 by operation of the lever 46,it drives the plate 34 in a counterclockwise direction about the pivot39. When the plate 35 is swung counterclockwise by the handle 46 itdrives the plate 34 clockwise. For effecting this driving relation, theplate 35 is provided with a downwardly projecting finger or boss 48which may be formed by depressing a portion of the metal of the plate35. The boss is disposed in a slot 49 in the plate 34. The slot is soarranged that upon swinging of the plate 35 clockwise andcounterclockwise, respectively, the boss 48 can engage the opposite endsor shoulders of the slot 49, respectively, and thereby positively drivethe plate 34 by the plate 35 to the fully rocked positions of the plate34. The length of the slot 49 is such that the boss 48 does not engagethe ends of the slots under normal driving of the plate 34 by the plate35 through the medium of dead center snap action springs, later to bedescribed.

In order to drive the cross bar 7 in response to operation of the lever46 and plates 34 and 35, a cross bar pin 50 is provided. For connectingthe pin 50 to the cross bar, the cross bar 7, as best illustrated inFIGS. 6 and 7, has a plurality of sockets 51 spaced apart from eachother axially of the cross bar. In the form illustrated, two sockets 51are provided so that the mechanism herein described can be reversed forright and left-hand operation and the pin can be made to associate withthe proper slot in the reversed position of the operating mechanism. Forthis selective right or left-hand arrangement each of the side walls 3is provided with a pivot pin 45 such as hereinbefore described. Sincethe plates 34 and 35 are symmetrical, instead of placing the operatinghandle 46 at the right, as in FIG. 8, it may be installed on the lefthand pivot 45 and the plates 34 and 35 rotated at about an axis parallelto the axes of the pivots 39 and 40 and reinstalled on the plate 2 inthe new position. In one position of the handle the plates, the crossbar pin 50 is disposed in one of the sockets 51 and in the oppositeposition of the handle and plates it is disposed in the other of thesockets 51. The cross bar pin 50 has a hooked end portion 50a which, asindicated in FIG. 3, is disposed in the selected one of the sockets 51,and has a straight end portion 50b extending therefrom which isconnected to the plates 34 so as to be dirven thereby.

If preferred, the cross bar pin 50 may be formed without the hooked end50a so as to have two straight end portions and may be connected to thecross bar 7 by one of a plurality of angularly disposed drilled holes.

To effect the driving connection with the pin, the plate 34 is providedwith an aperture 52 into which the straight end 5012 of the pin 50 fitswith operating clearance. The plate is provided with a passage 54 whichoverlies the aperture 52 in the plate 34 and is of such size as toprevent driving of the pin by the top plate 35 during initial driving ofthe top plate 35 by the handle in the switch opening direction todead-center position. When the top plate 35 passes slightly beyonddeadcenter position in the opening direction, the bottom plate isslightly past dead-center and snaps in the opening direction and drivesthe pin with a snap action to open the switch with a snap action.

Upon movement of the top plate in the closing direction, the pin 50 isengaged at once by the opposite end wall of the slot of the top plateand moved partway in the switch closing direction. As the plates passdeadcenter position of the bottom plate 34, the bottom plate snaps inthe switch closing direction and, by engagement of an end of its slotwith the pin 50, drives the pin with a snap action to close the switchwith a snap action.

The plates are arranged so that when the top plate 35 is moved a slightdistance beyond a dead-center position relative to the pivotal axes ofthe plates, they can be operated by dead-center springs to open or closethe switch with a snap action. For this purpose, the plate 34 isprovided with a post 56 and plate 35 is provided with a post 58. Mountedon the post 56 for rocking movement about an upright axis is a springholder 59. The spring holders 59 and 60 are provided with apertures 61and 62, respectively, which apertures are eqaually spaced from theirrespective posts. A pair of dead-center springs 64 and are provided, theopposite ends of the spring 64 being connected in one aperture 61 of thespring holder 59 and the corresponding aperture 62 of the spring holder60. Correspondingly, the dead-center spring 65 is connected to theopposite aperture 61 of the spring holder 59 and opposite aperture 62 ofthe spring holder 60. The axes of the posts 56 and 58 are such withrespect to the plates 34 and 35 and the dead-center springs that whenthe plate 35 is moved in either direction slightly beyond a dead-centerposition in which the posts 56 and 58 are aligned, parallel to the axesof the springs, the springs will become operative and move the plateswith a snap action relative to each other further in the direction inwhich the plate 35 was moved in passing dead center. Thus both platesare moved in a snap action. This snap action occurs before the boss 48engages either end wall of the slot 49, and hence the boss 48 and endwalls of the slot 49 are inoperative so long as the dead center springs64 and 65 are operative. However, the slot and boss provide a lostmotion positive drive between the plates. The lost motion is such that,though the boss 48 and ends of the slot 49 do not interfere with thenormal movement of the plates by the snap action of the dead centersprings, in event the springs become broken or fail to function, thelost motion can be taken up by movement of the plate 35 by the handle46. The slot 49 and boss 48 are so related that upon driving the plate35 to its final position in either direction by the handle 46, the plate35 drives the plate 34 to the final position to which the plate 34 wouldhave been driven by the dead-center springs had they remained effective.This lost motionpositive drive for opening and closing the switch incombination with a dead-center spring mechanism has the distinctadvantage in that failure of the snap action mechanism does not preventmanual and positive operation of the switch.

It is desirable in many instances to provide a fuse plate which canaccommodate fuses of different diameters and lengths. For this purpose,a fuse plate, as illustrated in FIGS. 1 and 2, is provided. The fuseplate comprises a body of rigid insulating material which is secured byscrews 71 to the body 1. For supporting the plate '70 in an uprightposition suitable stay braces 72 are connected at the lower end to theplate 70 and at the upper end to the plate 2. The plate 70 carries aplurality of line terminals 74 arranged in a row extending across theupper end of the plate and complementary load terminals 75 spaceddirectly therebeneath, respectively. The upper terminals 74 may beconnected to the terminals 18 heretofore described, respectively.However, when the fuse plate is to be used, the terminals 18 areunnecessary, and. the flexible conductors 16 may be connected directlyto the line terminals 74, respectively, at one end and to the blades 6at the opposite end in any conventional manner.

Suitable means are provided, as indicated at 76, for connecting the loadterminal 75 to external conductors. In order to hold selected types offuses, each of the line terminals 74 is provided with a plurality oftapped apertures 77 arranged in an upright row in suitably spacedrelation to each other. Each load terminal 75 is provided with tappedapertures 78 arranged in an upright row in alignment with the row ofapertures 77. Fuse clips 79 and 80 are provided for engaging oppositeends of a cylindrical fuse. For example, the clips 79 are adapted toengage the upper end of the fuse and the clips 80 are provided with abottom wall and are adapted to engage the lower end of the fuse. Eachclip 79 is connected to a line terminal by a suitable screw engaged in aselected one of the apertures 77 and each clip 80 is connected to acorresponding load terminal by a suitable screw engaged in a selectedone of the apertures 78. The particular apertures at which the fuseclips are connected are selected in accordance with the length of thefuse to be accommodated. The clips themselves are selected in accordancewith fuse diameter.

Thus, by shifting the selected fuse clips to different apertures, orusing fuse clips of different sizes, substantially any make of fusesuitable for use with this type and capacity of equipment can beaccommodated.

Having thus described my invention, I claim:

1. In a switch,

a support;

a set of stationary contacts carried thereby;

a movable cross bar;

means connecting the bar to the support for movement in oppositedirections, selectively;

complementary movable contacts carried by the cross bar and movablethereby to contact making position and to contact opening position,selectively, upon movement of the bar in said directions, respectively;

a pair of members;

parallel laterally offset pivots connecting the members,

respectively, to the support and supporting them in face to faceoverlapping relation, one member in front of the other with each memberextending from its pivot generally endwise toward the pivot of the othermember, each for swinging in opposite directions, selectively, along anarcuate path about the axis of its associated path;

drive means for driving the front member along its path in said oppositedirections, selectively;

lost motion connecting means drivingly connecting the front member tothe rear member so that the front member is movable from either end ofits path partway toward the other end of its path, in the selected oneof its directions of movement therealong, independently of the rearmember, to a dead center position, and so that the front member drivesthe rear member positively entirely to said other end of the path of therear member upon continued movement of the front member, in saidselected direction, beyond said dead center position while permittingcontinued movement of the rear member entirely to said other end of itspath in the selected direction, independently of the front member;

dead center spring means drivingly interconnecting the members andrendered operative, by moving the front member beyond said dead centerposition toward said other end of its path in the selected direc- 7 tionof movement, to drive the rear member with a snap action to its saidother end of its path, and means connecting the rear member to the crossbar for driving the cross bar in one of its directions of movement tocontact opening position upon movement of the rear member to one end ofits path and to contact closing position upon movement of the rearmember to the other end of its path.

2. The structure according to claim 1 wherein said lost motionconnecting means comprises a pair of shoulders on one member spacedapart from each other along its path;

shoulder means on said other member disposed between sald shoulders andspaced from each of them a distance such that the shoulder means aredisengaged from both of said shoulders during movement of the frontmember away from either end of its path to a position beyond dead centerposition, and engage the shoulder toward which the shoulder means ismoving upon continued movement of the front member in the samedirection.

3. The structure according to claim 1 wherein one member has a slottherein offset from its pivot;

the ends of the slot are the shoulders;

a finger is provided on the front plate and extends into the slot; and

the shoulder means are the opposite sides of the fingers facing towardsthe opposite ends of the slots, respectively.

4. The structure according to claim 1 wherein each member has a passagetherein elongated endwise of its ath; p the pivot of each member extendsthrough the passage of the other member with operating clearance; andthe point of connection of the dead center spring means with each memberis on the opposite side of the passage of the member from the pivot ofthat member.

5. The structure according to claim 1 wherein the means connecting therear member to the cross bar is a rigid rod connected at one end to thecross bar at a location in front of the front member and having itsother end received in a slot in the rear member and extending through apassage in the front member with such clearance that the trailing end ofthe slot in the direction of movement of the front member, in eitherselected one of said directions, engages the rod after movement of thefront member partway toward dead center position and thereby initi-'ates swinging of the rear member in the selected direction prior to thedead center spring means becoming operative.

6. The structure according to claim 5 wherein said members are plates,respectively, and are in face to face juxtaposition.

7. The structure according to claim 1 wherein said cross bar has aplurality of sockets therein, each with an open end in the peripheralwall of the cross bar;

each movable contact includes a body portion with a contact at one endand a shoulder spaced from the contact toward the opposite end;

said bodies are received in the sockets through the open ends thereof,respectively, said opposite ends foremost;

said shoulders of the bodies face toward the open ends of the sockets,respectively;

each socket has a shoulder therein facing away from its open end;

resilient snap fasteners are provided for the bodies, re-

spectively;

each snap fastener has a shoulder portion detachably engaged with theshoulder of its associated body and another shoulder detachably engagedwith the shoulder of its associated socket when the snap fastener is ina fastening position;

passage means are provided in the cross bar and communicate with thesockets, respectively, and afford access to the snap fasteners in thesockets by a tool so that each snap fastener can be individuallystrained transversely of its associated socket to a releasing positionwherein its said other shoulder is offset from the complementaryshoulder of its associated socket; and

each body has a concavity which can accommodate a part of its associatedsnap fastener in said released position so that the body and itsassociated snap fastener can be withdrawn endwise as a unit from theassociated socket.

8. In a switch,

a set of stationary contacts;

a movable cross bar of insulating material;

means supporting the cross bar for movement in opposite directionsselectively;

complementary movable contacts carried by the cross bar and movablethereby to contact making position and contact opening position,selectively, upon movement of said bar in said direction, respectively;

said bar having a plurality of sockets therein, each with an open end inthe peripheral wall of the cross bar;

each movable contact including a body portion with a contact at one endand a shoulder spaced from the contact toward the opposite end;

characterized in that:

said bodies are insertable in the sockets through the open ends thereof,respectively, said opposite ends foremost;

said shoulders of the bodies face toward the open ends of the sockets,respectively;

each socket has a shoulder therein facing away from its open end;

resilient snap fasteners are provided for the bodies,

respectively;

each snap fastener has a shoulder portion detachably engaged with theshoulder of its associated body and another shoulder detachably engagedwith the shoulder of its associated socket when the snap fastener is ina fastening position;

passage means are provided in the cross bar and communicate with thesockets, respectively, and afford access to the snap fasteners in thesockets by a tool so that each snap fastener can be individuallystrained transversely of its associated socket to a releasing positionwherein its said other shoulder is offset from the complementaryshoulder of its associated socket; and

each body has a concavity which can accommodate its associated snapfastener in said released position so that the body and its associatedsnap fastener can be withdrawn endwise as a unit from its associatedsocket.

9. The structure according to claim 8 wherein each body has a notchopening laterally of the cross bar with one side wall of the notchfacing the open end of the socket and providing the shoulder of thebody;

each snap fastener is a leaf spring having an end portion fitted withinthe notch and bearing against said side wall and having another portionextending outwardly of the notch and toward the outer end of the body;

said spring has a shoulder facing toward the bottom of the socket andengaging the shoulder of the body when the leaf spring is in stressedflexed position;

the concavity of the body faces the leaf spring and ac commodates aportion of the leaf spring when the leaf spring is stressed toward thebody a predetermined distance such that the shoulder of the leaf springis offset from the shoulder in the socket, whereby the body with theleaf spring can be removed through the open end of the socket while thespring is held in stressed condition by the tool.

10. The structure according to claim 8 wherein said movable contacts areswitch blades and are detachably received in the sockets, respectively,in the cross bar;

the snap action fasteners detachably engage the inner base in which thepair is rotated as a unit about an axis parallel to, and midway between,the axes of said pivots while maintained parallel to its first mountedposition, the drive member is detachably drivingly connected to saidfront member in the same driving relation; and

the means connecting the rear member to the cross bar is detachablyconnectable to the cross bar in two selective positions corresponding,respectively, to the tion and the snap fastener of the particular bladeis 10 released. 11. The structure according to claim 1 wherein supportsfor the drive means are mounted on the base at opposite ends of the pairof members, respectively;

two mounted positions of the pair of members.

References Cited UNITED STATES PATENTS the drive means include a drivemember connectable to 15 1 g; 232

said supports, selectively, and which, when so con- 1738406 12/1929Townsmld nected, is movable in opposite directions, selectively, 24684634/1949 Rowe along predetermined paths, respectively; 3194909 7/1965 p ithe drive member is arranged so that when it is connected to one of saidsupports and said pair of mem- 20 ROBERT K SCHAEFER Primary Examinerbers is in a first mounted position on the base, the drive member isdetachably drivingly connected to DAVID SMITH, Asslstant Examlner saidfront member; and when the drive member is connected to the other ofsaid supports and said pair of members is in a second mounted positionon the 25 74 973 200 67 US. Cl. X.R.

